A font metrics object, which gives information about the rendering
of a particular font on a particular screen. Note that the
implementations of these methods are inefficient, they are usually
overridden with more efficient toolkit-specific implementations.
Note to subclassers: Since many of these methods form closed
mutually recursive loops, you must take care that you implement
at least one of the methods in each such loop in order to prevent
infinite recursion when your subclass is used.
In particular, the following is the minimal suggested set of methods
to override in order to ensure correctness and prevent infinite
recursion (though other subsets are equally feasible):
When an application asks AWT to place a character at the position
(x, y), the character is placed so that its
reference point (shown as the dot in the accompanying image) is
put at that position. The reference point specifies a horizontal
line called the baseline of the character. In normal
printing, the baselines of characters should align.
In addition, every character in a font has an ascent, a
descent, and an advance width. The ascent is the
amount by which the character ascends above the baseline. The
descent is the amount by which the character descends below the
baseline. The advance width indicates the position at which AWT
should place the next character.
If the current character is placed with its reference point
at the position (x, y), and
the character's advance width is w, then the following
character is placed with its reference point at the position
(x + w, y).
The advance width is often the same as the width of character's
bounding box, but need not be so. In particular, oblique and
italic fonts often have characters whose top-right corner extends
slightly beyond the advance width.
An array of characters or a string can also have an ascent, a
descent, and an advance width. The ascent of the array is the
maximum ascent of any character in the array. The descent is the
maximum descent of any character in the array. The advance width
is the sum of the advance widths of each of the characters in the
array.
Determines the standard leading of the font described by
this font metric. The standard leading (interline spacing) is the
logical amount of space to be reserved between the descent of one
line of text and the ascent of the next line. The height metric is
calculated to include this extra space.
Determines the font ascent of the font described by this
font metric. The font ascent is the distance from the font's
baseline to the top of most alphanumeric characters. Some
characters in the font may extend above the font ascent line.
Determines the font descent of the font described by this
font metric. The font descent is the distance from the font's
baseline to the bottom of most alphanumeric characters with
descenders. Some characters in the font may extend below the font
descent line.
Gets the standard height of a line of text in this font. This
is the distance between the baseline of adjacent lines of text.
It is the sum of the leading + ascent + descent. There is no
guarantee that lines of text spaced at this distance will be
disjoint; such lines may overlap if some characters overshoot
either the standard ascent or the standard descent metric.
Gets the maximum advance width of any character in this Font.
The advance width is the amount by which the current point is
moved from one character to the next in a line of text.
Returns:
the maximum advance width of any character
in the font, or -1 if the
maximum advance width is not known.
Returns the advance width of the specified character in this Font.
The advance width is the amount by which the current point is
moved from one character to the next in a line of text.
Parameters:
ch - the character to be measured
Returns:
the advance width of the specified char
in the font described by this font metric.
Returns the advance width of the specified character in this Font.
The advance width is the amount by which the current point is
moved from one character to the next in a line of text.
Parameters:
ch - the character to be measured
Returns:
the advance width of the specified char >
in the font described by this font metric.
Returns the total advance width for showing the specified String
in this Font.
The advance width is the amount by which the current point is
moved from one character to the next in a line of text.
Parameters:
str - the String to be measured
Returns:
the advance width of the specified string
in the font described by this font metric.
charsWidth
public int charsWidth(char data[],
int off,
int len)
Returns the total advance width for showing the specified array
of characters in this Font.
The advance width is the amount by which the current point is
moved from one character to the next in a line of text.
Parameters:
data - the array of characters to be measured
off - the start offset of the characters in the array
len - the number of characters to be measured from the array
Returns:
the advance width of the subarray of the specified
char array in the font described by
this font metric.
bytesWidth
public int bytesWidth(byte data[],
int off,
int len)
Returns the total advance width for showing the specified array
of bytes in this Font.
The advance width is the amount by which the current point is
moved from one character to the next in a line of text.
Parameters:
data - the array of bytes to be measured
off - the start offset of the bytes in the array
len - the number of bytes to be measured from the array
Returns:
the advance width of the subarray of the specified
byte array in the font described by
this font metric.
Gets the advance widths of the first 256 characters in the Font.
The advance width is the amount by which the current point is
moved from one character to the next in a line of text.
Returns:
an array giving the advance widths of the
characters in the font
described by this font metric.
When an application asks AWT to place a character at the position
(x, y), the character is placed so that its
reference point (shown as the dot in the accompanying image) is
put at that position. The reference point specifies a horizontal
line called the baseline of the character. In normal
printing, the baselines of characters should align.
font
FontMetrics(Font)
bytesWidth(byte[], int, int)
font
FontMetrics
getFont